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The results raise the possibility that anti-H. pylori therapy may be used to help control or prevent diabetes in patients with chronic H. Pylori infection.

The bug that causes ulcers may also play a role in the development of type 2 diabetes, researchers said.

In two large cohorts, Helicobacter pylori colonization was positively associated with levels of glycosylated hemoglobin (HbA1c), a marker of impaired glucose tolerance, according to Yu Chen, PhD, and Martin Blaser, MD, both of New York University School of Medicine in New York City.

And the combination of H. pylori colonization and elevated body mass index was associated with higher HbA1c levels than either factor alone, Chen and Blaser reported in the April 15 issue of the Journal of Infectious Diseases.

The findings come from a cross-sectional analysis of two cohorts from the National Health and Nutrition Examination Surveys -- NHANES III, conducted from 1988 to 1994, and NHANES 1999-2000.

The surveys are the only two of the NHANES series in which lab data on H. pylori status were collected, the researchers noted. NHANES III also collected data on the presence or absence of the H. pylori virulence factor cytotoxin-associated gene A (cagA).

For this analysis, Chen and Blaser studied 7,417 participants in NHANES III (18 and older) and 6,072 in NHANES 1999-2000 (3 and older) who had data available on H. pylori, HbA1c, and sociodemographic and lifestyle variables.

The researchers found no association between H. pylori and history of self-reported diabetes.

However, after excluding people with a history of diabetes and controlling for potential confounders, colonization with H. pylori -- and especially a strain with the cagA gene -- was associated with HbA1c levels.

Specifically:

In NHANES 1990-2000, the 2,403 participants who were H. pylori-positive had a mean HbA1c level of 5.49%, compared with 5.40% among the 3,669 who were not colonized.

The difference was significant at P=0.02 and remained significant after self-reported diabetics and insulin users were excluded.

The association was significant among those 18 and older (at P<0.01) but lost significance among those under 18.

In NHANES III, the overall difference in HbA1c levels was non-significant, but became significant (at P<0.01) when diabetics and insulin users were excluded.

In both cohorts, there was also an interaction between H. pylori and body mass index of 25 or higher -- increased HbA1c associated with having both H. pylori and higher BMI was greater than the sum of their individual effects.

The interaction was significant at P=0.04 in NHANES III and P<0.01 in NHANES 1999-2000.

In NHANES IIII, which assessed levels of cagA, there was a progressive increase in average HbA1c levels when participants without H. pylori were compared with those with the bacterium but not cagA and those with both, the researchers said.

The trend overall was significant at P=0.02 and at P<0.01 when diabetics and insulin users were excluded.

The researchers cautioned that the study is cross-sectional and therefore can't say anything about causality. But reverse causation is unlikely, they said, simply because H. pylori is usually acquired in childhood.

The findings "could have important clinical and public health implications," commented Dani Cohen, PhD, of Tel Aviv University in Tel Aviv, Israel, and Khitam Muhsen, PhD, of the University of Maryland School of Medicine in Baltimore.

People with H. pylori colonization and a higher body mass index -- even if they have no symptoms -- may need treatment to prevent or control diabetes, they argued in an accompanying editorial commentary.

But, they cautioned, the findings need to be confirmed and more study is needed -- especially in the form of randomized trials -- to tease out the effect of H. pylori treatment on diabetes and HbA1c levels.

The study was supported by the NIH and the Diane Belfer Program in Human Microbial Ecology. The journal said the authors reported no conflicts.

The journal said the editorial commentary authors reported no conflicts.

Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner

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